The purpose of this study is to compare the effectiveness of delta-9-THC and Prochloroperazine (CompazineR) in controlling the nausea, vomiting, and loss of appetite frequently associated with cancer chemotheapy. Candidates for this study will be cancer inpatients and outpatients currently being cared for in the UCLA Departments of Medical and Surgical Oncology. Subjects will be of adult age and English speaking, not mentally disabled or pregnant. Approval will be obtained from the UCLA Human Subject Protection Committee and informed consent obtained from the patient. Drugs will be dispensed in double-blind fashion according to one of two randomly chosen schedules. Medication to be taken orally every 4 hours for 4 doses, beginning 1/2 hour before chemotherapy initiation. One of the 4 doses will be taken in the clinic and 3 at home. Unused medication will be returned to the pharmacy and careful records kept. Patients and the staff will estimate degree and duration of nausea and vomiting, as well as appetite and food intake. Mental status for mood will be assessed pre- and post-drug administration by patients and, in some cases, by a brief pre-chemotherapy psychiatric interview. Approximately 400 chemotherapy cycles will be included in this study, requiring the participation of approximately 200 patients.